In order to effectively use the mobile network resources, the 3rd Generation Partnership Project (3GPP) provides the MBMS service. The MBMS service is a technique of transmitting data from one data source to multiple destinations, which implements the share of the network (including the core network and the access network) resources, and improves the utilization ratio of the network resources (especially the air interface resources). The MBMS defined in the 3GPP is able to not only implement the pure text and low speed message classified multicast and broadcast, but also implement the broadcast and multicast of the high speed multimedia service, and provide various and rich video, audio and multimedia service, which complies with the trend of the future mobile data development and provides a better service prospect for the development of the 3G.
In the LTE, the MBMS service can use a way of the multicast mode, which is called as a Multicast/Broadcast over Single Frequency Network (MBSFN) transmitting mode. The MBMS service sent by the multicast mode is also called as the MBSFN service. The same coding after modulating format can be used in multiple cells. The same physical resource is used to send the same content. The features of the multi-cell transmission of MBMS include: 1) synchronization transmission in the MBSFN area; 2) supporting the multi-cell MBMS transmission combination; 3) the Multicast traffic Channel (MTCH) and the Multicast Control Channel (MCCH) are mapped into the MCH transport channel in the Point to Multi-point (p-T-m) mode; 4) the MBSFN synchronization area, the MBSFN area, MBSFN transmission, the advertisement and the reserved cell are all semi-statically configured by the operation and maintenance. Thus, the User Equipment (UE) of multiple cells can receive multiple MBMS data with the same content and perform the Single Frequency Network (SFN) combination, thereby being able to improve the gain of the received signal.
Multiple cells using the same physical resource and using the MBSFN transmission mode to send the same MBMS service compose one MBSFN area. In the practical LTE networking, several MBSFN services exist in one MBSFN area, and all these MBSFN services belonging to the same MBSFN area are called as one MBSFN service group, and that is to say, one MBSFN service group only belongs to one MBSFN area. One MBSFN area includes multiple cells, and each cell is configured with one completely same MBSFN service group. The MTCH, scheduling information and the corresponding MCCH of multiple MBSFN services in the same MBSFN area can be multiplexed into one Multicast Channel (MCH). The MCCH and MTCH are logical channels, and the MCH is a transport channel.
In the related art, the MCH is mapped into the Physical Multicast Channel (PMCH) of the physical channel, and the MCH and the PMCH are the one-to-one mapping.
The related art introduces the MBSFN Subframe Allocation Pattern occasion (MSAP occasion) used for indicating the multicast subframe resources occupied by the MTC in a period. One MCH channel allocates one or more MBSFN subframe in one or more MBSFN frames through the MSAP. The MBSFN subframe refers to the subframe sent by the multicast mode, and the MBSFN frame refers to the frame including the MBSFN subframe.
In the related art, the base station notifies the UE of the resource allocation information related to the MCH through the MCCH message in the radio interface, and said resource allocation information includes information such as the resource allocation period, the particular location/number of the resources occupied by each MCH and so on. For example, in a method, the resource allocation periods of all the MCHs in the MBSFN area corresponding to this MCCH, the information of all the MBSFN subframes multiplexed by all the MCHs in this MBSFN area, and the MBSFN subframe resources for time division multiplexing in the resource allocation period of different MCHs are indicated in the MCCH message. One particular allocation example is as shown in FIG. 1, and three MCHs are time division multiplexed to one group of MBSFN subframes in one resource allocation period, wherein the MCH1 occupies the subframes with numbers from 1 to 4, the MCH2 occupies the MBSFN subframes with numbers from 5 to 9, and the MCH3 occupies the MBSFN subframes with numbers from 10 to 14. Said MBSFN subframe numbers refer to the unified numbers of the MBSFN subframe shared by all the MCH channels in one MBSFN area in said resource allocation period.
For the dynamical multiplexing of the MBMS service, the related art also introduces the concept of scheduling period. The scheduling period refers to the time period periodically configured for the radio interface. In one scheduling period, one MTCH or the data of one MBMS service continuously occupy the MBSFN subframe resource of the MCH bearing this MBMS service until all the service data of the service required to be sent in this scheduling period are completely sent. Data for different services might also be sent in the same MBSFN subframe. That is to say, service data of different services may be cascaded together to be sent in the same Media Access Control (MAC) Packet Data Unit (PDU). The above service sending order is notified to the user equipment through the MCCH channel. FIG. 2 shows one example of sending the scheduling information and the data of two services S1 and S2 in dynamical multiplexing in one scheduling period in a MCH, wherein the scheduling information is used for indicating the location information of the MBSFN subframe where the data of each MBMS service born on the MCH channel is located in the scheduling period. The user equipment is only required to receive the service data at its interested particular MBSFN subframe by indicating the location information of the service data to avoid reading the MBSFN subframe bearing other services.
There are following a plurality of particular methods for indicating the scheduling information: 1, the start subframe location of the service; 2 the end subframe location of the service, and at this point, the UE obtaining the start location information of the posterior service by obtaining the end location of the previous service; 3, the number information of the subframes occupied by the service, and at this point, the UE obtaining the start subframe location of one service by accumulating the number of subframes occupied by all the services before said one service in one MCH.
The scheduling information is sent by one of following ways. 1. The scheduling information is sent by being born in the logical channel MSCH, and the MSCH is born in the MCH to send. 2. The scheduling information is sent by being born in the MAC Control Element (CE), and the MAC CE is born in the MCH to send.
In one of existing methods for implementing the synchronization sending of the MBMS service data among a plurality of network elements, one synchronization protocol processing, i.e., Synchronization (SYNC) protocol, is provided. This SYNC protocol comprises following processing.
In step 1, the upper layer network element sends the MBMS service data packet to various lower layer network elements, and this service data packet carries the service data and includes the time stamp information, the data packet serial number information and accumulated service data length information and so on. The upper layer network element identifies one or more continuous service data packets with the same time stamp information, and these data packets identified with the same time stamp composes one data burst, which is also called as the synchronization sequence. The difference of time stamps of two adjacent synchronization sequences is the length of the synchronization sequence, or is called as a SYNC period.
At present, there are two ways for configuring the time stamp information of each data packet, and one is to include the reference time information when the synchronization sequence starts to be sent at the radio interface in each data packet contained in the synchronization sequence, the other is to include the reference time information when the previous synchronization sequence starts to be sent at the radio interface in each data packet included in the synchronization sequence.
At the end of each synchronization sequence, the upper layer network element also sends a kind of the SYNC control frame, which only includes information of the total number of the data packets of the previous synchronization sequence and the total length of the data packets, for use by the lower layer network elements detecting the end of one synchronization sequence and obtaining the total data length and the total number of data packets of one synchronization sequence.
In step 2, for the service data packets in one synchronization sequence, the lower layer network elements send the service data packets in sequence at the radio interface in the scheduling period corresponding to the time stamp carried in the service data packet.
According to the sizes of the SYNC period and the scheduling period, the length of a plurality of synchronization sequences can correspond to one scheduling period, and that is, a plurality of synchronization sequences sent by the upper layer network element are mapped into one scheduling period at the radio interface, and the data of the plurality of synchronization sequences of one service are cascaded by the RLC layer to implement the continuous sending in the scheduling period. Or, the length of one synchronization sequence also can correspond to one or more scheduling periods, and that is, one synchronization sequence sent by the upper layer network element is mapped into resources of one or more continuous scheduling periods at the radio interface to be sent.
The above upper layer network elements can be a Broadcast Multicast Service Center (BMSC), a Gateway GPRS Support Node (GGSN), a Serving GPRS Support Node (SGSN), a multimedia broadcast multicast service gateway namely a Media Gateway (MGW), or other network element entities for implementing functions of the above upper layer network element. The lower layer network element can be a Radio Network Controller (RNC), a NodeB, eNB, or node B+ in the High Speed Packet Access+(HSAP+) network (NB+), or other network element entities for implementing functions of the above lower layer network element.
In the existing synchronization method, network architecture for implementing the multi-network element coordination resource allocation is also provides. In this architecture, a central coordination network element is defined. This network element implements the following functions: coordinating multiple lower layer network elements to allocate the same radio interface resources for the same traffic or transport channel; coordinating the multiple lower layer network elements to implement the synchronously scheduling and sending of the service data; coordinating multiple lower layer network elements to synchronously update MCCH so as to implement the synchronization sending of the MCCH. In the LTE system, the above coordination network element is a Multi-cell/multicast Coordination Entity (MCE), and in the UMTS system, the above coordination network element is a primary RNC.
FIG. 3 shows a relation diagram of the above upper layer network element, the coordination network element and the lower layer network element. The solid line in FIG. 3 is used for representing the transmission of the data packet and the control packet, and the dotted line is used for representing the control signalling connection.
In one existing related art, different services can be configured with different scheduling periods. According to the difference of the quality of service and the service traffic features, the service with a large service speed change is configured with a larger scheduling period so as to obtain the gain of the smooth service traffic. The service with a small service speed change can be configured with a smaller scheduling period so as to shorten the delay of receiving the service by the UE. But for the radio interface resource allocation, i.e., the MBSFN subframe resource configuration of the MCH, multiple different MCHs can be configured with the same resource allocation period so as to achieve the object of simplifying the signalling and reducing the overhead of the signalling.
Considering the consistence of the mapping from the scheduling period to the radio resource allocation period, the scheduling period should be the integral times of the resource allocation period of the MCH. At this point, one scheduling period is represented as the length of multiple continuous resource allocation periods at the radio interface. The service data that is required to be sent in the scheduling period is sent on the radio resource allocated in the multiple resource allocation periods.